The promising results have emerged from a new study of 1,700 men with advanced prostate cancer, which causes the death of 500 patients in Ireland every year.

The drug enzalutamide also allowed an average of 17 extra healthy months before the need for chemotherapy.

Previously, the drug, which has few side-effects, was only tested on men who already had chemotherapy and had exhausted most other options.

The latest study, presented to the American Society of Clinical Oncology Genitourinary Symposium in San Francisco, showed that over three years, men on the drug were on average 29pc less likely to die than those on a placebo.

The risk of the disease worsening was cut by 81pc. Men did not need chemotherapy on average for 28 months compared with 10.8 months for the control group.

Enzalutamide is under review by the National Cancer Control Programme to determine its future availability in Ireland.

Researchers have described the findings as very exciting.

It comes as a study of Irish men undergoing chemotherapy for prostate cancer reveals the distressing side-effects they can suffer, which can leave them fatigued and depressed.

Family members confirm that the patient's quality of life can be seriously damaged.

The research, which involved interviews with the loved ones of prostate cancer patients, was carried out by the drug company Janssen during Movember, the fundraising event held in November in which men sport moustaches for cancer research.

They reported that the most common side-effects were nausea and vomiting, followed by hair loss, fatigue and loss of appetite.